1. Field of the Invention
This invention relates in general to planing boat hulls and in particular to those having shapes to reduce drag.
2. Background Information
There is known in the prior art a single step hull design that has been used on some boats and on amphibian aircraft to reduce drag in part by increasing the planing angle over what it would have been without the step (see FIG. 5). This hull design has the effect of reducing the wetted area but is of limited effectiveness since the planing angle of attack cannot be held at its optimum to achieve lowest drag over a wide range of speeds. This single step hull design does have the advantage of providing two lifting surfaces, one at the bow and the other near the stern.
Boat hulls with two side by side planing surfaces, such as some catamarans are used to improve lateral stability rather than reduce drag. Most catamarans are sail powered and use a displacement hull rather than a planing hull. The hull design which is the subject of our invention is best suited for planing hulls with a length to width ratio greater than 4 and would be particularly well suited to a planing catamaran hull in which each planing surface generally has a very high length to width ratio.